This invention relates to an assembly for hitching a trailer to a towing vehicle and for automatically actuating the hydraulic brakes of the trailer when the towing vehicle slows and the trailer tends to surge forward and overrun the towing vehicle. More particularly, the invention relates to an assembly having a forward unit which is adapted to be coupled removably to a hitch ball on the towing vehicle and which is pivotally interconnected with a rear unit adapted to be carried on the trailer. When the trailer surges forwardly, the rear unit moves forwardly relative to the forward unit and pivots relative to the forward unit about a laterally extending axis to cause a member on the forward unit to actuate a master cylinder on the rear unit. Upon being actuated, the master cylinder pressurizes the wheel cylinders of the trailer to apply the trailer brakes.
An assembly of the foregoing type is commonly referred to as a surge brake actuator. An actuator whose forward and rear units are pivotally interconnected in the manner described above possesses several advantages over actuators having telescoping units or having units which are interconnected by parallel links. For example, a surge brake actuator with pivotally interconnected units generally achieves a higher gain or mechanical advantage. Also, such an actuator generally is shorter in length, lighter in weight and more economical to manufacture than actuators with telescoping or parallel linked units.